Integrated-optical microsystem based on organic semiconductors

ABSTRACT

The monolithic integration of all key photonic components ( 11 - 16 ) of an integrated-optical microsystem ( 1 ) based on organic semiconductors is disclosed. Examples of such components ( 11 - 16 ) are light sources ( 11 ), photodetectors ( 12 ), photovoltaic power generators ( 12 ), field-effect transistors ( 13, 14 ), resistors, capacitors ( 15 ), or waveguiding structures ( 11, 12 ). The components ( 11-16 ) are arranged on a common substrate ( 20 ), are compatible with each other, can be manufactured simultaneously and can be operated simultaneously. At least one of the components ( 11 - 14 ) comprises a layer ( 23 ) of organic semiconductor material. Each component ( 11 - 16 ) comprises a plurality of layers ( 21 - 26 ), at least one of which ( 21 ) has identical physical and chemical characteristics in at least two components ( 11 - 16 ). The large number and diversity of photonic devices that can be monolithically integrated allows a higher degree of integration, of functionality and of system complexity than was practical with the state of the art.

FIELD OF THE INVENTION

[0001] This invention relates to integrated-optical microsystems, andmore particularly to an integrated-optical microsystem based on organicsemiconductors and to a method for manufacturing the same. Anintegrated-optical microsystem comprises at least two differentelectronic, photonic and/or micromechanic components arranged on acommon substrate. Important examples of such components aremonochromatic (laser) or polychromatic (LED) light sources,photodetectors, photovoltaic power generators, p-channel and n-channelfield-effect transistors, resistors, capacitors, light-guiding orwave-guiding structures, or derived sensing devices for the measurementof pressure, magnetic or electric fields, chemical or bio-chemicalsubstances, etc. Applications include self-powered posters or businesscards, millimeter-thin large-area scanners and electronic paper.

BACKGROUND OF THE INVENTION

[0002] Known techniques for the fabrication of microsystems rely onhybrid methods for the integration of the different functionalitiesrequired. Especially photonic microsystems, in which it is necessary togenerate and detect light, consist of sub-systems that are manufacturedwith very different materials, using different types of technology.Light is generated usually with compound semiconductors such as GaAs,InP or InGaAsP. Light is often detected with inorganic semiconductorssuch as Si or Ge. Electronic circuits are realized with Si-basedtechnologies such as complementary metal oxide semiconductor (CMOS) orbipolar. Passive optical components such as lenses, prisms or mirrorsare realized with glass. Microoptical elements such as microlens arraysor diffractive optical components are fabricated with plastic materials,while the bodies and cases of complete systems are manufactured withmetals or plastics.

[0003] It is known that passive optical functions can be combined withmechanical functions, using injection molding of polymers to produceso-called “optical monoblocks” (cf. P. Seitz, “Real-time opticalmetrology for microsystems fabrication”, Proc. SPIE, Vol. 3825, pp104-110, 1999). These integrated systems combine all passive opticalelements (refractive, diffractive, reflective and obstructive) and allmechanical elements for assembly, mounting and fixing in one piece ofpolymer that can be fabricated, for example, with a singleinjection-molding process.

[0004] It is also known that photosensitive elements, electronic devicesand circuits can be combined monolithically into “smart pixels” and“smart image sensors”, preferably using silicon (cf. P. Seitz, “SmartImage Sensors: An Emerging Key Technology for Advanced OpticalMeasurement and Microsystems”, Proc. SPIE, Vol. 2783, pp. 244-255,1996). Due to the semiconductor properties of silicon it is difficult,however, to generate light within the same material used for the rest ofthe photosensitive and electronic devices.

[0005] The difficulty of generating light with silicon can be overcomeby employing compound semiconductors, which make it possible tomonolithically integrate photosensitive, photoemissive, analog anddigital electronic elements in so-called optoelectronic integratedcircuits (OEICs) (cf. U. Kehrli, D. Leipold, K. Thelen, J. E. Epler, P.Seitz and B. D. Patterson, “Monolithically Integrated-opticalDifferential Amplifiers for Applications in Smart Pixel Arrays”, IEEE J.Quantum Electronics, Vol. 32 (5), pp. 770-777, 1996).

[0006] Another, hybrid approach for overcoming the difficulty ofgenerating light with silicon is described in U.S. Pat. No. 6,307,528 byD. Yap. A silicon substrate contains electronic circuits, and an organicsemiconducting layer is deposited on top, with which light can beemitted under control of the underlying electronic circuits.

[0007] A hybrid solution for an optical head assembly based on anorganic electroluminescent light-emitting array is described in U.S.Pat. No. 6,297,842 by M. Koizumi et al. The electronic circuits arecontained in a silicon substrate, on top of which an organicsemiconductor is deposited that generates light under control of theunderlying circuits. These hybrid elements are then mounted on a printedcircuit board to form a complete optical head assembly.

[0008] U.S. Pat. No. 5,770,446 by T. Sasaki et al. describes themonolithic combination of laser, optical amplifier, optical waveguide,optical modulator and optical switch with a suitable selection ofinorganic compound semiconductors such as InP and InGaAsP. Devices areformed with a sequence of selective crystal growth processes usingdemanding metallo-organic vapor phase epitaxy, photolithographicdefinition of structures and suitable etching steps.

[0009] U.S. Pat. No. 6,228,670 by K. Kudo describes the monolithiccombination of a highly integrated array of laser diodes, waveguides andoptical amplifiers. Devices are formed with a sequence of selectivecrystal growth processes using demanding metallo-organic vapor phaseepitaxy, photolithographic definition of structures and suitable etchingsteps.

[0010] From U.S. Pat. No. 6,300,612 by G. Yu it is known thatphotosensors based on organic semiconductors can be realized; thisreference teaches the fabrication of a two-dimensional arrangement ofindividually addressable photodiodes. Since no means is foreseen forproviding local amplification or electronic buffering, the noiseperformance of the described organic photosensors must be at least oneorder of magnitude below the performance of prior-art silicon-basedphotosensors.

SUMMARY OF THE INVENTION

[0011] It is an object of the invention to provide an integrated-opticalmicrosystem based on organic semiconductors and a method ofmanufacturing such integrated-optical microsystem which overcome thelimitations of the prior art. In particular, it is an object tomanufacture the complete optical microsystem with one single process,avoiding cost for assembly and further hybrid system integration.Another object is to scale up the manufacturing process to very largesurfaces of square meters. Still another object is to significantlyreduce the production costs of optical microsystems compared with theprior art. Yet another object is to shape the resulting microsystems inthree dimensions after an essentially planar fabrication. Still anotherobject is to achieve a higher degree of integration, of functionalityand of system complexity than with the prior art.

[0012] These and other objects are solved by the integrated-opticalmicrosystem and the manufacturing method as defined in the independentclaims. Advantageous embodiments are defined in the dependent claims.

[0013] The invention discloses the monolithic integration of all keyphotonic components of an integrated-optical microsystem based onorganic semiconductors, in particular of monochromatic (laser) orpolychromatic (LED) light sources, photodetectors, photovoltaic powergenerators, p-channel and n-channel field-effect transistors, resistors,capacitors, light guiding or wave guiding structures, as well as derivedsensing devices for the measurement of pressure, magnetic or electricfields, chemical or bio-chemical substances, etc. The term “monolithicintegration” means in this connection that the components

[0014] are arranged on a common substrate,

[0015] are compatible with each other,

[0016] can be manufactured simultaneously and

[0017] can be operated simultaneously.

[0018] The integrated-optical microsystem according to the inventioncomprises a substrate and a plurality of components arranged on saidsubstrate. At least a first of said components comprises a layer oforganic semiconductor material. Said first component and a second,different component are monolithically integrated on said substrate.

[0019] In a preferred embodiment of the integrated-optical microsystemaccording to the invention, said first component and said secondcomponent each comprise a plurality of layers, and said first componentand said second component each comprise a corresponding layer withidentical physical and chemical characteristics, and preferably withidentical thicknesses and identical chemical and physical consistencies.Preferably said first component and said second component each comprisea plurality of corresponding layers, said corresponding layers beingmutually arranged in the vertical direction in the same order. Saidlayers are, e.g., selected from the group consisting of: a first and asecond electrically conductive layer, one of said electricallyconductive layers being a hole injection layer and one of saidelectrically conductive layers being an electron injection layer; anelectrical insulation layer; an organic semiconductor layer; and alight-guide or wave-guide layer.

[0020] The method for manufacturing an integrated-optical microsystemaccording to the invention comprises the steps of providing a substrateand arranging a plurality of components on said substrate. At least afirst of said components comprises a layer of organic semiconductormaterial. Said first component and a second, different component aremonolithically integrated on said substrate.

[0021] In a preferred embodiment of the method according to theinvention, the process of monolithic integration of said first componentand said second component comprises the fabrication of a plurality oflayers, and a corresponding layer is fabricated simultaneously in saidfirst component and said second component. Preferably the process ofmonolithic integration of said first component and said second componentcomprises the fabrication of a plurality of corresponding layers in saidfirst component and said second component, each corresponding layerbeing fabricated simultaneously in said first component and said secondcomponent. Said layers are selected, e.g., from the group consisting ofa first and a second electrically conductive layer, one of saidelectrically conductive layers being a hole injection layer and one ofsaid electrically conductive layers being an electron injection layer;an electrical insulation layer; an organic semiconductor layer; and alight-guide or wave-guide layer.

[0022] The present invention of integrated-optical microsystems based onorganic semiconductors overcomes the limitations of the described stateof the art in all of the following respects:

[0023] Since the fabrication process is monolithic, the complete opticalmicrosystem can be fabricated with it, avoiding any cost for assemblyand further hybrid system integration.

[0024] The fabrication process can be scaled up to very large surfacesof square meters, and all technological steps to perform this are withinthe state of the art. This allows the fabrication of large-area opticalmicrosystems or the simultaneous fabrication of a very large number ofsmaller optical microsystems.

[0025] Because of the economy of scale and the obsolete additionalassembly steps, production costs of optical microsystems fabricatedaccording to this invention can be significantly lowered.

[0026] The resulting microsystems can be arbitrarily shaped in threedimensions after essentially planar fabrication, provided a flexiblesubstrate is used.

[0027] The large number and diversity of photonic devices that can bemonolithically integrated allows a higher degree of integration, offunctionality and of system complexity than was practical with the stateof the art.

[0028] Throughout this document, terms such as “light”, “optical” or“photo . . . ” refer to any kind of electromagnetic radiation, such asvisible light, infrared (IR) or ultraviolet (UV) radiation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The invention is described in greater detail hereinafter relativeto the attached schematic drawings.

[0030]FIG. 1 shows a schematic cross sections through anintegrated-optical microsystem according to the invention, with variousintegrated-optical components.

[0031]FIG. 2 shows a schematic circuit diagram of a first embodiment ofa display according to the invention.

[0032]FIG. 3 schematically shows a pixel of an active display accordingto the invention.

[0033]FIG. 4 shows a schematic perspective view of a preferredimplementation of the active pixel of FIG. 8.

[0034]FIG. 5 shows a schematic circuit diagram of a second embodiment ofa display according to the invention.

[0035]FIG. 6 schematically shows a preferred embodiment of an activepixel of a detector according to the invention.

[0036]FIG. 7 shows a circuit diagram of a simple self-powered displayaccording to the invention.

[0037]FIG. 8 schematically illustrates an integrated, self-powereddisplay according to the invention.

[0038]FIG. 9 shows a schematic diagram of an integrated-opticalmicrosystem according to the invention.

[0039]FIG. 10 schematically illustrates a monolithic sheet scanner ofelectronic paper according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0040]FIG. 1 shows a schematic cross section through anintegrated-optical microsystem 1 according to the invention. Themicrosystem 1 comprises at least two different electronic, photonicand/or micromechanic components 11-16 arranged on a common substrate 20.The examples of such components 11-16 shown in FIG. 1 are: an integratedlight-emitting device 11 (FIG. 1(a)); an integrated photodetector orphotovoltaic cell 12 (FIG. 1(b)); an integrated n-channel field-effecttransistor (FET) 13 (FIG. 1(c)); an integrated p-channel FET 14 (FIG.1(d)); an integrated capacitor 15 (FIG. 1(e)); and/or an interconnectregion 16 between two conductive layers (hole and electron injectors)(FIG. 1(f)). Of course, this list of examples is not exhaustive, and aperson skilled in the art having knowledge of the invention will be ableto derive many other components, including resistors, light-guiding orwave-guiding structures, or sensing devices for the measurement ofpressure, magnetic or electric fields, chemical or bio-chemicalsubstances, etc. These components may further be combined with otherelectronic, photonic and/or micromechanic components which arewell-known from “classical” integrated-circuit (IC) technology.

[0041] The substrate 20 may be transparent or opaque, and may be rigidor flexible, depending on the envisaged application. Examples ofstructures usable as substrates 20 are the well-known silicon wafer,thin stainless steel foils, or transparent plastics such as polyester(PET, Mylar®), polyimide (Kapton®), polyamides (Nylon®), polypropyleneor polyethylene.

[0042] The components 11-16 arranged on the common substrate 20 arecompatible with each other, can be manufactured simultaneously and canbe operated simultaneously. They are built up from a set of elements,typically structured layers 21-26 of various materials, examples ofwhich are given in the following with reference to FIG. 1. Referencesign 21 denotes a hole injection layer that is transparent or opaque.

[0043] Reference signs 22 and 24 denote a first and second insulationlayer, respectively. Reference sign 23 denotes an active organicsemiconductor layer. Reference sign 25 denotes an injection layer thatis transparent or opaque. Reference sign 26 denotes a light-guiding orwave-guiding layer. Of course, this list of examples is not exhaustive,and a person skilled in the art having knowledge of the invention willbe able to derive many other elements for building up the components,including diffusion from solution or gas phase and ion implant layers.

[0044] As is evident from FIG. 1, a component does not necessarilycontain all of the set of elements 21-26, and the elements 21-26 may bedifferently structured in different components 11-16. However, due tothe simultaneous manufacturing of the components 11-16, thecorresponding layers 21-26 in each component 11-16 have the samethickness, the same chemical and physical consistency and are mutuallyarranged in the vertical direction z in the same order. Thesecharacteristics clearly distinguish a monolithic microsystem 1 accordingto the invention from a hybrid microsystem known from the prior art.

[0045] In the following, the steps and the process flow of a preferredembodiment of the manufacturing method according to the invention areexplained with reference to FIG. 1.

[0046] (a) A planar substrate 20 is selected and provided, whoseproperties depend on the envisaged application of the opticalmicrosystem to be manufactured. If the microsystem needsthree-dimensional shaping after fabrication, then the substrate 20 mustbe flexible, otherwise it can be rigid. If light needs to penetrate thesubstrate 20, the substrate 20 must be optically transparent in thecorresponding wavelength range, otherwise it can be opaque. Opaquesubstrate materials include crystalline silicon wafers or thin stainlesssteel foils; transparent substrate materials include polyester (PET,Mylar®), polyimide (Kapton®), polyamides (Nylon®), polypropylene orpolyethylene.

[0047] (b) The substrate 20 is covered with a first conductive layer 21that is capable of injecting holes into an organic semiconductor. Apreferred material is indium tin oxide (ITO), which has also theadvantage of being transparent. To improve hole transport and injectionproperties, the conductive hole-injecting material 21 can optionally becovered with a suitable hole-transporting layer such as PEDOT,poly(3,4-ethylenedioxythiophene).

[0048] (c) The first conductive layer 21 can act as the gate electrodeof an n-channel field-effect transistor (FET). For this purpose, thefirst conductive layer 21 must be electrically insulated from subsequentcovering layers with a first thin (1 to 200 nm thick) insulator 22.Examples of suitable insulating materials include SiO₂ (silicondioxide), Si₃N₄ (silicon nitride), as well as any inorganic or organicsemiconductors with a band gap of at least 2.5 eV. Geometric definitionof the n-channel FET gates can be realized, for example, with knownlithography-based techniques, such as wet etching, dry etching or liftoff.

[0049] (d) An active material 23 of an organic semiconductor isdeposited, such as PPP—poly (para phenylene), PPV—poly (para phenylenevinylene), Alq3—aluminum tris-(8, hydroxyquinoline), tetracene orpentacene. The deposition is effected with suitable techniques such asspin coating (for semiconducting polymers) or vacuum evaporation (forsmall semiconducting molecules) on the substrate 20 and/or the alreadydeposited layers 21, 22. The preferred thickness of the organicsemiconductor layer 23 is between 10 nm (to avoid photon losses andreduced quantum efficiencies) and 1000 nm (to respect the low mobilitiesand short life times of organic semiconductors).

[0050] To improve the electronic mobility of the organic material 23,either globally or locally in selected regions, orientation techniquescan be employed, as described in T. Uchida and H. Seki, “Surfacealignment of liquid crystals”, in “Liquid Crystals Applications andUses”, Vol. 3, Birendra Badahur (Ed.), Chapter 5, pp. 2-64, WorldScientific Singapore, 1992, ISBN 981-02-0403-5. Mechanical, optical ormagnetic orientation techniques are known for this purpose. The increaseof electronic mobility in a selected direction is a useful property forthe realization of FETs that are capable of faster switching andcarrying higher currents, as well as for high-brightness light sourcessuch as superluminescent diodes or electrically pumped lasers.

[0051] If the organic semiconductor 23 has a high electronic mobility,the different, monolithically produced components 11-16 (such as shownin FIG. 1) must be separated from each other by restricting the organicsemiconductor layers 23 to selected areas. Knownsemiconductor-processing techniques can be employed for this purpose. Ifthe electronic mobility of the organic semiconductor 23 is low and thegeometric distance between different components 11-16 is large, nogeometrical separation might be necessary because the organicsemiconductor material's 23 electrical resistance between components11-16 is so high that it effectively insulates the components 11-16 fromeach other.

[0052] (e) In areas where the organic semiconductor 23 is used as thebulk of a p-channel FET, the organic semiconductor layer 23 must beelectrically insulated from subsequent covering layers 25, 26 with asecond thin (1 to 200 nm thick) insulator 24. Examples of suitableinsulating materials include SiO₂ (silicon dioxide), Si₃N₄ (siliconnitride), as well as any inorganic or organic semiconductors with abandgap of at least 2.5 eV. Geometric definition of the p-channel FETgates can be realized, for example, with known lithography-basedtechniques, such as wet etching, dry etching or lift off.

[0053] (f) The low-lying layers 21-24 are covered with a secondconductive layer 25 that is capable of injecting electrons into anorganic semiconductor. Preferred materials are calcium (Ca) or aluminum(Al). To improve electron transport and injection properties of theelectron-injecting material 25, an additional layer can be depositedunder the electron-injecting material 25. Preferred electron-transportmaterials 25 include Alq₃, aluminum-tris(8-hydroxichinoline), and PBD,(2-(4-biphenylyle)-5-(4-tert-butyle-phenyle)-1,3,4-oxadiazole.

[0054] The conducting electron-injection layer 25 is also used as anelectronic interconnect. Its geometric definition can be realized, forexample, with known, lithography-based techniques used in semiconductortechnology.

[0055] (g) In areas where the conducting electron-injection material 25and hole-injection material 21 should be electrically connected, it isnecessary to provide the required openings in all layers 22-24 above thehole-injecting layer. This can be realized, for example, with known,lithography-based techniques used in semiconductor technology.

[0056] (h) If light needs to be transported along the horizontaldirection x of the substrate 20, a layer 26 of optically transparentmaterial can be deposited and geometrically defined. The index ofrefraction of this layer 26 should be close to the index of refractionof the electron-injection material 25, which should be opticallytransparent for this purpose. This ensures efficient optical couplingbetween the light-guiding structures and the organic semiconductor 23,in which light is generated or detected.

[0057] If only a very narrow spectral range of light needs to betransported, a wave-guide structure can be employed, requiring a matchedlayer thickness of 100 to 2000 nm. For a wider spectral range, asproduced for example by an LED, a light-guiding structure with athickness of 1 micrometer up to several millimeters is more appropriate.

[0058] Preferred materials for the waveguide or light guide 26 arepolymers such as PMMA (poly methyle acrylate), PC (poly carbonate),polyimide or PVC (poly vinyl chloride), or Sol-Gelmaterials such asOrmocer®. The geometrical definition of these waveguiding orlight-guiding structures preferably occurs with a replication processsuch as hot embossing, UV casting, rubber stamping or injection molding.

[0059] The geometrical definition of areas with polymeric organicsemiconductors is not only possible with the lithography-basedtechniques known from semiconductor technology. Organic semiconductors23 can also be selectively deposited in thin layers by alternate,inexpensive techniques such as ink jet printing, screen printing,rubber-stamping or micro-molding (cf. H. Sirringhaus, T. Kawase and R.H. Friend, “Emerging Methods for Micro- andNanofabrication—High-Resolution Ink-Jet Printing of All-PolymerTransistor Circuits”, MRS Bulletin—Materials Research Society, Vol. 26,pp. 539-543, 2001).

[0060] The manufacturing method described above is only a preferred,simple example. A person skilled in the art having knowledge of theinvention will be able to derive further processes for manufacturing amicrosystem 1 according to the invention. The common characteristics ofthese manufacturing methods is the capability of developing controlledthicknesses of material (several 10 nm up to a few micrometers) incontrolled geometrical patterns (spatial resolution of some 10 nm toseveral 10 micrometers).

APPLICATION EXAMPLES

[0061] 1. Active-Pixel LED and Display

[0062] In an active-pixel-display unit cell 110, one terminal 112 of alight-emitting-diode (LED) structure 111 is connected to a fixed-voltageline 113, while the other terminal 114 is connected via a transistorswitch 116 to a variable-voltage line 115, as schematically illustratedin FIG. 2. A two-dimensional array 100 of one or more of suchLED/transistor unit cells 110 is provided with at least one row-selectline 120 that is connected to all gates of the transistor switches 116in a row. The transistor switches 116 of each row have their draincontacts connected to a column line 115. Each column line 115 isconnected via a column-select transistor 130 to a common signal line140.

[0063]FIG. 3 shows a preferred realization of anactive-pixel-LED-display unit cell 110, making use of the fabricationprocess explained with reference to FIG. 1. A preferred implementationof the same active-pixel-LED-display unit cell 110 is shown in aperspective view in FIG. 4. In FIGS. 3 and 4, identical reference signsare used for elements already introduced with reference to FIGS. 1 and2.

[0064] An individual LED 111 is lighted by connecting it to the signalline 140. This is accomplished by applying the correct potential to therow-select lines 120: in the case of p-channel transistors, a negativepotential must be applied, in the case of n-channel transistors, apositive potential must be applied to render the switch transistors 116conductive. The column line 115 of the LED 111 that needs to be lightedis connected via the appropriate column-select transistor 130 to thecommon signal line, by applying a suitable potential to the gate of thiscolumn-select transistor 130, in the same way as for the row-selecttransistors 116. In this way, an electrically conductive path is createdfrom the fixed-voltage line 113 to the signal line 140 through the LED111 that needs to be lighted.

[0065] The intensity of the LED is controlled by the amount of currentthat flows through it, and this can be controlled with the signal line.If the total resistance of the current path is well known in advance (ifthe fabrication process is well controlled), then it is sufficient toapply a suitable potential to the signal line to achieve a predictablebrightness of the LED. Otherwise, an electronic circuit is required inthe signal that sources the required amount of current (so-calledcurrent-source circuit).

[0066] If only one LED 111 needs to be illuminated at a given time, alltransistors are switched off except for the corresponding row-selecttransistor 116 and the corresponding column-select transistor 130. Ifseveral LEDs in a rectangular area need to be lighted with the samebrightness and at the same time, then all corresponding row-selecttransistors 116 and column-select transistors 130 can be switched on,while all other transistors are switched off. The current that flowsthrough the signal line is N times as large as the current that flowsthrough one LED, where N is the number of LEDs that are lighted at thesame time.

[0067] By switching on certain patterns of the row-select transistors116 and column-select transistors 130, it is also possible to light upcorresponding two-dimensional patterns of LEDs that need not to berectangular. By sequentially switching on all LEDs in thetwo-dimensional array 100 at fixed time intervals, complete sequences ofmoving images can be displayed. If the potential on the signal line 140is varied only between two voltages, then only line images aredisplayed; if the potential on the signal line is varied continuously,gray-level images are displayed. Grey-level images can also be displayedwith a fixed potential or a fixed current value at the signal line 140,by employing different times for which the individual LEDs are switchedon: a bright LED is switched on for a longer time than a darker LED.

[0068] If the two-dimensional array 100 of active-pixel LEDs 110consists of a large number of LEDs, then an individual LED 111 is onlyswitched on for a comparatively short time. This leads to a loweroverall brightness of the created image. This limitation can be overcomewith the circuit 200 shown in FIG. 5, making it possible to illuminateall LEDs 211 with their appropriate brightness at the same time. This isachieved by supplying each LED 211 with a current-source transistor 217,where the current-source transistors 217 of all pixels 210 are tied tothe same potential, preferably to ground on a ground line 218. The gateof each current-source transistor 217 can be programmed to a specificvoltage with the row-selection mechanism 216, 220, column-selectionmechanism 230, 215 and signal-line voltage mechanism 240 described abovewith reference to FIGS. 2-4. To improve the voltage-retention times inthe pixels 210, an additional capacitance 219 can be added at the gateof the current-source transistor 217 in each pixel 210. The otherterminal of the LED 211 is connected to a fixed-voltage line 213, inanalogy to FIGS. 2-4.

[0069] 2. Active-Pixel Photosensor and Image Sensor

[0070] Excellent image sensors based on photodiodes can be realized withthe active-pixel-sensor (APS) architecture for silicon-basedphotosensors. Such an APS pixel 310 and an image sensor based on it canbe realized with the process according to the invention, as illustratedin FIG. 6. A photodiode 311 is reverse-biased to a reference voltage ona reference-voltage line 313 with a reset transistor 312, the gate ofwhich is connected to a reset line 314. The other terminal of thephotodiode 311 is connected to a ground line 318. The incident lightpartly discharges the photodiode 311 to a voltage value that can bemeasured with a source follower comprising a source-follower transistor317 and a load resistor that is common to all APS pixels 310 at the endof a common signal line 315. The individual pixels 310 are connected tothe common signal line 315 with a pass transistor 316, whose gate isconnected row-wise to a row-selection line 320. Addressing occurssimilarly to the active-pixel LEDs 210 described above with reference toFIGS. 2-5.

[0071] 3. Active Lighting for Advertising, Fashion and Security

[0072] Since it is possible, according to the invention, to produceintegrated optoelectronic systems also on large surfaces at low cost,there are many applications in advertising, fashion and security, onvarious surfaces such as business cards, letterheads, large and smallposters, shopping bags, garments (T-shirts, windbreakers, pullovers,jeans, sneakers, shoes, etc.), household items, cars, traffic signs,signal bands, and many others.

[0073] A very simple self-powered display 400 is shown in FIG. 7. Itconsists of one or a series connection of one or more photoemissiveelements 411 and photovoltaic elements 412.1, 412.2.

[0074] A preferred realization of an integrated self-powered display 500is illustrated in FIG. 8. It comprises one or several photovoltaicelements or cells 510 that are either connected in parallel or inseries. A series connection allows for the simple generation of highervoltages. The photovoltaic cells 510 can be realized as simplerectangular shapes, or they can be realized in complex forms such asletters, digits or images. It is possible to print information 511 onthe photovoltaic elements 510, as long as there is sufficient free spacefor the photovoltaic generation of the required electric power.

[0075] The photovoltaic elements 510 are connected to an electroniccircuit 520 that carries out one or more of the following functions:voltage conversion, voltage regulation, current limitation, powermanagement, clock generation, flashing effects, etc. The electronics 520can be connected to an integrated capacitive device 530 for temporarypower filtering and storage (during periods of insufficient illuminationof the photovoltaic element).

[0076] The electronics 520 feeds power to one or more photoemissivesurfaces 540 that can be arbitrarily shaped. It is possible to printopaque structures on the photoemissive surfaces 540.

[0077] The electronics 520 can drive the photoemissive structures 540either continuously or temporally intermittently for effects such asflashing, running lights or simulated movement. It is also possible tointegrate a display 100, 200 as described above with reference to FIGS.2 or 5, on which moving images can be shown.

[0078] 4. Integrated-Optical Microsystems for Measurements

[0079] A large number of optical measurement techniques exist that canbe implemented with the fabrication process according to the invention.They share the basic principle of operation that a light source isemitting light under the control of an electronic circuit, this lightinteracts with the object under study to produce light that carries thedesired information, a photodetector detects this light, and anelectronic circuit extracts the information from the detected light andpasses it on for further processing.

[0080] The integrated-optical microsystems according to the inventionare especially useful for the realization of many types of opticalmeasurement principles, because the microsystem can be bent into a largevariety of three-dimensional shapes after planar fabrication, provided aflexible substrate is used.

[0081] A particularly powerful class of integrated-optical microsystemsthat had to be realized until now with hybrid fabrication methods isdescribed in R. E. Kunz, “Totally Integrated-optical Measuring Sensors”,Proc. SPIE, Vol. 1587, pp. 98-113, 1992. These and otherintegrated-optical microsystems 600 can be implemented with the processdescribed in this invention, as illustrated in FIG. 9.

[0082] A power-supply unit 610 provides electric power, either bydrawing it from a storage device such as a battery or a chargedcapacitor, or by producing it with an integrated photovoltaic devicecomprising a series connection of one or more photodiodes underillumination that are used as photovoltaic elements (cf. FIG. 7,reference signs 412.1, 412.2). This electric power is managed anddistributed by an electronic control circuit 620 for controlling thedevice 600, converting voltages, limiting electrical current, acquiringand processing signals, managing power, controlling the display ofresults, etc. The circuit 620 powers one or more light-emitting devices640 (LEDs, superluminescent diodes, laser diodes, etc.). If required bythe optical measurement principle, emitted light 641 can already bemodulated by the driving circuit 620, for example by carrying out atemporal amplitude modulation. The emitted light 641 is guided with asuitable light guide or waveguide 650 near the surface of theintegrated-optical microsystem 600 to a region of interaction 660. Thelight 641 interacts with the objects 661 under study according to theeffects described in R. E. Kunz's paper, e.g., it is influenced by themeasurand 661 in intensity, polarization, wavelength etc. The light 642that is guided further carries now information in the form of changedposition, modified intensity, modified polarization, modifiedwavelength, modified contrast, altered temporal modulation properties,etc. At the end of the light guide or waveguide 650 are arranged one ormore photodetectors 670 that detect the light 642 carrying the desiredinformation. Depending on the type of information, a suitable type ofdetection principle must be chosen, as described in the literature.

[0083] The measurement results are processed and interpreted by theelectronic circuit 620, producing a measurement result that is eitherdisplayed locally or that is transmitted outside the optical microsystem600 with a suitable interface 680, using electrical, optical or othertransmission principles. The interface may, e.g., have electricalcontacts or an optical interface device comprising at least onephotoemissive and one photodetecting element. A display 690 of themicrosystem 600 can be realized as one or more indicator LEDs of thesame or of different color, as numeric (seven-segment) display, asalphanumeric display or as a display with full graphic capabilityaccording to FIGS. 2 or 5. The co-integration of one or several of thesevarious types of displays with the optical microsystem 600 is possiblewith the fabrication process according to the invention and illustratedwith reference to FIG. 1.

[0084] 5. Sheet Scanner (Ultimate Flat-Bed Scanner)

[0085] An optoelectronic scanner that is as thin as a sheet of paper canbe realized with the components described above, according to theinvention. It comprises a two-dimensional array 700 of one or more unitcells 710, each realized as a combination of one or more active-pixellight-emission cells 110 (or 210) such as discussed with reference toFIG. 2 (or 5, respectively), and one or more APS light sensing cells 310such as discussed with reference to FIG. 6. The array 700 isschematically illustrated in FIG. 10. Each active-pixel LED 110 and eachAPS sensor pixel 310 can be addressed individually, making use ofappropriate row-selection and column-selection mechanisms describedabove.

[0086] For each scanner unit cell 710 the scanning process consists ofresetting first the APS pixel 310, then switching on the pixel LED 110for illumination of the local environment for a certain time, andfinally reading out the APS pixel 310. If a reflecting (bright) objectwas lying next to the scanner cell 710, then a high reflection valuewill be read; if the object was locally dark (in printed areas), a lowerreflection value will be read. The two-dimensional pattern of reflectionvalues represent an image of the object (e.g., a document) close to thesurface of the scanner cells 710. For improved depth of field andimproved geometric registration, microlenses or gradient-index (GRIN)lenses can be placed over the scanner unit cells 710, as is known fromfacsimile scanning machines.

[0087] Depending on the application, the available electrical power andthe desired scanning time, the LEDs 110 are lighted sequentially (one ata time), larger numbers such as complete lines or extended areas arelighted at a time, or all LEDs 110 are lighted simultaneously.

[0088] 6. Electronic Paper

[0089] The sheet scanner 700 described above and illustrated in FIG. 10can also be used as electronic paper which, together with an appropriatepen, is part of an electronic writing equipment. The pen for writing onthe paper can either be active or passive.

[0090] A passive pen has a well-reflecting tip, realized for examplewith retroreflecting microprisms or microspheres, or with a metallic orwhite coating. The sheet scanner is operated as for the scanning purposedescribed above. At the position of the writing pen's tip a highreflection value will be read. The corresponding pixel LED 110 will beilluminated and stays illuminated, showing the locations where the penhas been.

[0091] The scanning operation with a passive pen consumes a significantamount of electrical power because each position measurement requiresthe illumination of a large number of pixel LEDs.

[0092] By using an active pen, the power consumption can besignificantly reduced. The active pen has a small area at the tip with adiameter of, e.g., 5 mm or less, from which light is emitted. This lightis generated in the pen, for example with an LED. The scanning operationcomprises the steps of resetting the APS sensing pixels 310 and readingout the values after a short exposure time of, e.g., less than 100 ms.In locations where the pen's tip has emitted enough light to create anappreciable signal in the APS pixels 310, the pixel LEDs 110 areswitched on continuously, to indicate where the pen has been.

[0093] To reduce the scanning time and the power consumption, it issufficient to scan the environment of the pen's last position, since thepen will be moved with limited speed over the scanning surface. Onlywhen the pen has been lifted from the scanning surface is it necessaryto inspect again the complete area.

[0094] 7. Pocket calculator, data entry and display system A monolithicpocket calculator, data entry and data display system can be realizedwith the components described above, according to the invention.

[0095] The keys are realized as scanner unit cells 710, as describedabove. When a finger comes close to the surface, the local reflectionincreases, and it can be detected that “the key has been pressed”. Thedisplay unit can either consist of traditional seven-segment numericLEDs or a fine-grained rectangular array of LEDs for higher-resolveddisplay of numerals, characters and images. An integrated electroniccircuit provides the power management, the key reading functions, drivesthe display, carries out all necessary calculations and provides forelectrical, optical or other interfaces, as described above.

[0096] This invention is not limited to the preferred embodimentsdescribed above, to which variations and improvements may be made,without departing from the scope of protection of the present patent.

[0097] List of Reference Signs

[0098]1 Microsystem

[0099]11 Integrated light-emitting device

[0100]12 Integrated photodetector or photovoltaic cell

[0101]13 Integrated n-channel FET

[0102]14 Integrated p-channel FET

[0103]15 Integrated capacitor

[0104]16 Interconnect region

[0105]20 Substrate

[0106]21 Hole injection layer

[0107]22 First insulation layer

[0108]23 Active organic semiconductor layer

[0109]24 Second insulation layer

[0110]25 Injection layer

[0111]26 Light-guiding or wave-guiding layer

[0112]100 Active-pixel display

[0113]110 Active-pixel-display unit cell

[0114]111 LED structure

[0115]112, 114 Terminals of LED structure

[0116]113 Fixed-voltage line

[0117]115 Variable-voltage line

[0118]116 Row-select transistor

[0119]120 Row-select line

[0120]130 Column-select transistor

[0121]140 Common signal line

[0122]200 Active-pixel display

[0123]210 Active-pixel-display unit cell

[0124]211 LED structure

[0125]213 Fixed-voltage line

[0126]215 Variable-voltage line

[0127]216 Row-select transistor

[0128]217 Current-source transistor

[0129]218 Ground line

[0130]219 Capacitance

[0131]220 Row-select line

[0132]230 Column-select transistor

[0133]240 Common signal line

[0134]310 APS pixel

[0135]311 Photodiode

[0136]312 Reset transistor

[0137]313 Reference-voltage line

[0138]314 Reset line

[0139]315 Common signal line

[0140]316 Pass transistor

[0141]317 Source-follower transistor

[0142]318 Ground line

[0143]320 Row-select line

[0144]400 Self-powered display

[0145]411 Photoemissive element

[0146]412 Photovoltaic element

[0147]500 Self-powered display

[0148]510 Photovoltaic element

[0149]511 Information on photovoltaic element

[0150]520 Electronic circuit

[0151]530 Integrated capacitive device

[0152]540 Photoemissive surface

[0153]600 Integrated-optical microsystem

[0154]610 Power-supply unit

[0155]620 Electronic control circuit

[0156]640 Light-emitting device

[0157]641 Emitted light

[0158]642 Guided light carrying information

[0159]650 Light guide or waveguide

[0160]660 Region of interaction

[0161]661 Measurand

[0162]670 Photodetector

[0163]680 Interface

[0164]690 Display

[0165]700 Sheet scanner

[0166]710 Unit cell

1. An integrated-optical microsystem (1) comprising a substrate (20) anda plurality of components (11-16) arranged on said substrate (20), atleast a first of said components (11) comprising a layer (23) of organicsemiconductor material, characterized in that said first component (11)and a second, different component (12-16) are monolithically integratedon said substrate (20).
 2. The integrated-optical microsystem (1)according to claim 1, wherein said first component (11) and said secondcomponent (12-16) each comprise a plurality of layers (21-26), and saidfirst component (11) and said second component (12-16) each comprise acorresponding layer (21) with identical physical and chemicalcharacteristics, and preferably with identical thicknesses and identicalchemical and physical consistencies.
 3. The integrated-opticalmicrosystem (1) according to claim 2, wherein said first component (11)and said second component (12-16) each comprise a plurality ofcorresponding layers (21-26), said corresponding layers (21-26) beingmutually arranged in the vertical direction (z) in the same order. 4.The integrated-optical microsystem (1) according to claim 2, whereinsaid layers (21-26) are selected from the group consisting of a first(21) and a second (25) electrically conductive layer, one of saidelectrically conductive layers being a hole injection layer (21) and oneof said electrically conductive layers being an electron injection layer(25), an electrical insulation layer (22, 24), an organic semiconductorlayer (23), and a light-guide or wave-guide layer (26).
 5. Theintegrated-optical microsystem (1) according to claim 4, wherein saidhole injection layer (21) comprises indium tin oxide, said electroninjection layer (25) comprises calcium or aluminum, said electricalinsulation layer (22, 24) comprises silicon dioxide and/or siliconnitride, said organic semiconductor layer (23) comprises poly (paraphenylene), poly (para phenylene vinylene), aluminum tris-(8,hydroxyquinoline), tetracene or pentacene, and/or said light-guide orwave-guide layer (26) comprises poly methyle acrylate, poly carbonate,polyimide or poly vinyl chloride or a sol-gel material.
 6. Theintegrated-optical microsystem (1) according to claim 4, wherein saidlayers (21-26) are selectively deposited on said substrate (20) in thefollowing order: first a first electrically conductive layer (21) sothat said first electrically conductive layer (21) is closest to saidsubstrate, then said electrical insulation layer (22, 24) and/or saidorganic semiconductor layer (23) in an arbitrary order, then a secondelectrically conductive layer (25), and then said light-guide orwave-guide layer (26) so that said light-guide or wave-guide layer is atthe largest distance from said substrate (20).
 7. The integrated-opticalmicrosystem (1) according to claim 6, wherein said first componentcomprises a structure with a first electrically conductive layer (21)deposited closest to said substrate (20), an organic semiconductor layer(23) deposited above said first electrically conductive layer (21), asecond electrically conductive layer (25) deposited above said organicsemiconductor layer (23), and preferably a light-guide or wave-guidelayer (26) deposited above said second electrically conductive layer(25), and is usable as an integrated light-emitting device (11), anintegrated photodetector or an integrated photovoltaic cell (12).
 8. Theintegrated-optical microsystem (1) according to claim 6, wherein saidfirst component comprises a structure with a first electricallyconductive layer (21) deposited closest to said substrate (20), anelectrical insulation layer (22) deposited above said first electricallyconductive layer (21), an organic semiconductor layer (23) depositedabove said electrical insulation layer (22), and two separate secondelectrically conductive layers (25) each deposited above said organicsemiconductor layer (23), and is usable as an integrated n-channelfield-effect transistor (13), said first electrically conductive layer(21) being the gate and said two separate second electrically conductivelayers (25) being the drain and source.
 9. The integrated-opticalmicrosystem (1) according to claim 6, wherein said first componentcomprises a structure with two separate first electrically conductivelayers (21) each deposited closest to said substrate (20), an organicsemiconductor layer (23) deposited above said first electricallyconductive layers (21), an electrical insulation layer (24) depositedabove said organic semiconductor layer (23), and a second electricallyconductive layer (25) deposited above said electrical insulation layer(24), and is usable as an integrated p-channel field-effect transistor(14), said two separate first electrically conductive layers (21) beingthe drain and source and said second electrically conductive layer (25)being the gate.
 10. The integrated-optical microsystem (1) according toclaim 6, wherein said second component comprises a structure with afirst electrically conductive layer (21) deposited closest to saidsubstrate (20), an electrical insulation layer (22) deposited above saidfirst electrically conductive layer (21), and a second electricallyconductive layer (25) deposited above said electrical insulation layer(22), and is usable as an integrated capacitor (15).
 11. Theintegrated-optical microsystem (1) according to claim 6, wherein saidsecond component comprises a structure with a first electricallyconductive layer (21) deposited closest to said substrate (20), twoseparate electrical insulation layers (22) each deposited above saidfirst electrically conductive layer (21), and a second electricallyconductive layer (25) deposited above said electrical insulation layers(22), and is usable as an interconnect region (16) between said firstelectrically conductive layer (21) and said second electricallyconductive layer (25).
 12. The integrated-optical microsystem (1)according to claim 1, wherein said substrate (20) is selected from thegroup consisting of crystalline silicon wafers, thin stainless steelfoils, polyesters such as PET, Mylar®, polyimides such as Kapton®,polyamides such as Nylon®, polypropylene or polyethylene.
 13. Theintegrated-optical microsystem (1) according to claim 1, wherein saidcomponents (11-16) are selected from the group consisting ofmonochromatic and polychromatic light sources (11), photodetectors (12),photovoltaic power generators (12), n-channel (13) and p-channel (14)field-effect transistors, resistors, capacitors (15), light-guiding andwave-guiding structures (11, 12), interconnect regions (16) between twoelectrically conductive lines, and derived sensing devices for themeasurement of pressure, magnetic or electric fields or chemical orbio-chemical substances.
 14. An active-pixel light-emitting diodedisplay (100, 200) comprising a fixed-voltage line (113, 213), avariable-voltage line (115, 215), a switch transistor (116, 216), and alight-emitting diode structure (111, 211), a first terminal (112) ofwhich is connected to said fixed-voltage line (113, 213) and a secondterminal (114) of which is connected via said switch transistor (116,216) to said variable-voltage line (115, 215), characterized in thatsaid light-emitting diode structure (111, 211) and said switchtransistor (116, 216) are components of an integrated-opticalmicrosystem (1) according to claim
 1. 15. An active-pixel photosensor orimage sensor (300) comprising a ground line (318), a reference-voltageline (313), a signal line (315), a source-follower transistor (317)connecting said reference-voltage line with said signal line, a resettransistor (312), and a photodiode (311), a first terminal of which isconnected to said ground line (318) and a second terminal of which isconnected via said reset transistor (312) to said reference-voltage line(313) and to the gate of said source-follower transistor (317),characterized in that said source-follower transistor (317), said resettransistor (312) and said photodiode (311) are components of anintegrated-optical microsystem (1) according to claim
 1. 16. A sheetscanner (700) comprising a light-emitting unit and a light-detectingunit, characterized in that said light-emitting unit comprises anactive-pixel light-emitting diode display cell (110, 210) according toclaim 14 and said light-detecting unit comprises an active-pixelphotosensor or image sensor cell (310) according to claim
 15. 17. Anelectronic writing equipment comprising a pen and a writing surface,characterized in that said pen has a reflecting or light-emitting tipand said paper is an electronic paper comprising a sheet scanneraccording to claim
 16. 18. A pocket calculator comprising a key unit, adisplay unit, and an integrated electronic circuit, characterized inthat said key unit comprises a sheet scanner according to claim
 16. 19.An active lighting device (400, 500) comprising a photoemissive element(411, 540) and a photovoltaic element (412.1, 412.2, 510) characterizedin that said photoemissive element (411, 540) and said photovoltaicelement (412.1, 412.2, 510) are components of an integrated-opticalmicrosystem (1) according to claim
 1. 20. An integrated-optical sensor(600) comprising a light-emitting device (640), a light guide orwaveguide (650) for guiding light (641) emitted by said light-emittingdevice (640), a region of interaction (660) in a vicinity of said lightguide or waveguide (650), and a photodetector (670) for detecting light(642) exiting from said region of interaction (660), characterized inthat said light-emitting device (640), said light guide or waveguide(650) and said photodetector (670) are components of anintegrated-optical microsystem (1) according to claim
 1. 21. A methodfor manufacturing an integrated-optical microsystem (1), comprising thesteps of: providing a substrate (20) and arranging a plurality ofcomponents (11-16) on said substrate (20), at least a first (11) of saidcomponents (11-16) comprising a layer (23) of organic semiconductormaterial, characterized in that said first component (11) and a second,different component (12-16) are monolithically integrated on saidsubstrate (20).
 22. The method according to claim 21, wherein theprocess of monolithic integration of said first component (11) and saidsecond component (12-16) comprises the fabrication of a plurality oflayers (21-26), and a corresponding layer (21) is fabricatedsimultaneously in said first component (11) and said second component(12-16).
 23. The method according to claim 22, wherein the process ofmonolithic integration of said first component (11) and said secondcomponent (12-16) comprises the fabrication of a plurality ofcorresponding layers (21-26) in said first component (11) and saidsecond component (12-16), each corresponding layer (21-26) beingfabricated simultaneously in said first component (11) and said secondcomponent (12-16).
 24. The method according to claim 22, wherein saidlayers (21-26) are selected from the group consisting of a first (21)and a second (25) electrically conductive layer, one of saidelectrically conductive layers being a hole injection layer (21) and oneof said electrically conductive layers being an electron injection layer(25), an electrical insulation layer (22, 24), an organic semiconductorlayer (23), and a light-guide or wave-guide layer (26).
 25. The methodaccording to claim 24, wherein said hole injection layer (21) comprisesindium tin oxide, said electron injection layer (25) comprises calciumor aluminum, said electrical insulation layer (22, 24) comprises silicondioxide and/or silicon nitride, said organic semiconductor layer (23)comprises poly (para phenylene), poly (para phenylene vinylene),aluminum tris-(8, hydroxyquinoline), tetracene or pentacene, and/or saidlight-guide or wave-guide layer (26) comprises poly methyle acrylate,poly carbonate, polyimide or poly vinyl chloride or a so-gel material.26. The method according to claim 24, wherein said layers (21-26) areselectively deposited on said substrate (20) in the following order:first a first electrically conductive layer (21), then said electricalinsulation layer (22, 24) and/or said organic semiconductor layer (23)in an arbitrary order, then a second electrically conductive layer (25)and then said light-guide or wave-guide layer (26).